A sensor (also called detector) is a device that measures a physical quantity and converts it into a signal which can be read by an observer or by an instrument. For example, a mercury-in-glass thermometer converts the measured temperature into expansion and contraction of a liquid which can be read on a calibrated glass tube. A thermocouple converts temperature to an output voltage which can be read by a voltmeter. For accuracy, most sensors are calibrated against known standards.
In biomedicine and biotechnology, sensors which detect analytes having a biological component, such as cells, protein, or nucleic acid are called biosensors. Biosensors can be used for both in vitro and in vivo applications.
Typically, biosensors are exposed to a biological specimen, such as blood or urine and are used to detect predetermined analytes within the biological specimen. The biosensor may then be exposed to a transducer or detector element which may work in a physiochemical manner using a sensing medium such as light, electricity, piezoelectric, electrochemical or the like. In any event, the transducer or detector element transforms a signal from the biosensor into another signal that can be more easily measured and quantified. The signal produced by the transducer or detector element may be provided to a reader device having associated electronics, signal processors and/or a display to provide the results in a user readable format. For example, the results can be provided on a graphical display.
In any event, one type of biosensor that has been used in the past is based upon technology including an interdigitated sensor array which achieves amplification of a sensor signal. The interdigitated sensor array is provided with at least two microelectrodes, both of which have fingers which are spaced apart and interleaved in an interdigitated fashion. Each of the microelectrodes is provided with a relatively large trace connected to a plurality of relatively fine traces. Exemplary interdigitated sensor arrays have been described in a variety of articles, such as Large-area interdigitated array microelectrodes for electrochemical sensing, Sensors and Actuators, Adam E. Cohen, and Roderick R. Kunz (2000) pgs. 23-29; Digital Simulation of the Measured Electrochemical Response of Reversible Redox Couples at Microelectrode Arrays: Consequences Arising from Closely Spaced Ultramicroelectrodes, Allen J. Bard et al., Anal. Chem. 1986, 58, 2321-2331; and United States Patent Application Number 2009/0084686, filed on Feb. 27, 2008; and United States Patent Application Number 2007/0145356, filed on Dec. 25, 2005.
Limitations in the trace dimensions (the width of the interdigitated fingers) and space dimensions (the edge-to-edge distance of the interdigitated fingers) are encountered using standard screen printing, electrodeposition and laser ablation approaches to manufacturing the interdigitated sensor arrays. For these reasons, in the past, the interdigitated sensor arrays have been fabricated using semi-conductor type fabrication techniques including photolithography using substrates suitable for use in semiconductor fabrication. Exemplary prior art substrates include silicon dioxide, glass, ceramic, a semiconductor material, or a flexible material. See for example, paragraph [0023] of United States Patent Application Number 2007/0145356.
However, to Applicant's knowledge, there has not been a cost-effective method for fabricating a biosensor with an interdigitated sensor array that makes such biosensor available to be mass produced and widely used as a disposable sensor for testing biological specimens, such as blood and urine. It is to such a method and apparatus for cost-effectively producing biosensors that the present disclosure is directed.